1. Field of the Invention
The present invention relates to a hydraulically actuated and controlled diaphragm pump in a boiler feed water pumping system. More particularly, the invention is directed to a relatively vibration free diaphragm pump whose rate of pumping can be controlled to vary the amount of feed water delivered to a boiler or steam generator.
2. Description of the Prior Art
The prior art has utilized various forms of hydraulic fluid systems for supplying and controlling hydraulic fluid under pressure to hydraulic motors which drive pistons or plungers in a pump mechanism. For example, positive displacement pumps have been widely used when it is desired to move a large volume of fluid at a relatively high pressure. Diaphragm proportioning pumps have been utilized generally in applications which require the pumping of fluids at accurately controlled rates. A frequent problem in both forms of pumps has been the effects of surging or pressure pulsations which are capable of creating destructive vibrations which produce noise and tend to induce destructive stresses in the pump. The pressure surges generally develop from the increase of velocity imparted to the fluid by the sudden releasing or movement of the fluid in the system.
In the field of boiler steam generators having, for example, a 10 million BTU output per hour with a steam operating pressure of 65 to 350 psi, a diaphragm type of water pump has been utilized driven by an electric motor. The electric motor drives reciprocating pistons within the pump housing which, in turn, drive the diaphragms hydraulically by the oil displaced by the reciprocating pistons. One section of the pump can be stopped by bypassing the oil through a solenoid bypass valve thereby controlling the pump output. Tubular water columns can separate the check valve housings from the pump heads to keep excessive temperature from the diaphragms. Snubbers absorb pressure pulsations to insure a stabilized pump delivery. The amount of water delivered to the coil of the steam generator is actually regulated by a water bypass valve capable of returning a portion of the water to the pump inlet. An appropriate water bypass pressure regulator can maintain a constant pressure at the bypass valve inlet to assure constant flow characteristics through the valve to control the flow rate.
The patent literature contains numerous examples of diaphragm pumps such as the Hetz U.S. Pat. No. 3,494,294, Booth U.S. Pat. No. 2,732,127, Bowman U.S. Pat. No. 2,593,255, Carver U.S. Pat. No. 2,948,221, and Schmidt U.S. Pat. No. 2,646,000. Likewise, numerous patents have been granted for various forms of pumping systems such as Jackson U.S. Pat. No. 3,405,654, Telford U.S. Pat. No. 3,260,245 Carr Jr., et al U.S. Pat. No. 3,101,058 and Krute U.S. Pat. No. 3,022,738. Many of these prior art patents are directed to diaphragm pumps and feed water systems for special requirements that are relatively expensive. There is still a demand for a relatively inexpensive, durable, vibration free diaphragm pump for use in feed water supply systems to boilers and the like.